Conventionally, various measuring devices have been used for determining a concentration of a desired gas component in a measurement gas. A known device of measuring a NOx concentration in a measurement gas such as a combustion gas, for example, is a sensor having a Pt-containing electrode and a Rh-containing electrode formed on an oxygen ion conductive solid electrolyte layer, such as zirconia (ZrO2) (see Japanese Patent Application Laid-Open No. 8-271476 and Japanese Patent Application Laid-Open No. 2004-37473, for example).
A sensor element used for detecting a predetermined gas component in a measurement gas in a gas sensor as disclosed in Japanese Patent Application Laid-Open No. 8-271476 or Japanese Patent Application Laid-Open No. 2004-37473 is manufactured by forming a predetermined circuit pattern on each of the plurality of ceramics green sheets including zirconia, which is an oxygen ion conductive solid electrolyte, as a ceramics component, by a screen printing or the like, laminating and integrating the plurality of ceramics green sheets to obtain a laminated body which is cut into an unit of element, and then burning.
The ceramics green sheets are subjected to various processes to manufacture the sensor element, as described the above. Therefore, deformation such as flexure or distortion caused by the process in manufacturing steps may be generated in the manufactured sensor element.
Specifically, a piece of the laminated body which has been cut into an unit of element (sensor element before burning) is to be shrunk by burning (burning shrinkage). This burning shrinkage is larger than shrinkage generated in other steps (e.g., a step of printing a circuit pattern on a ceramics green sheet, a step of drying after printing step or the like). Therefore, in the burning step of the steps of manufacturing the sensor element, deformation such as flexure or distortion is generated more easily than in other steps.
In the case where large deformation is generated in the manufactured sensor element due to shrinkage in the burning step or the like, the gas sensor manufactured using the sensor element may not be assembled accurately, or the measurement accuracy of the sensor may be affected. Deformation of the sensor element generated by burning shrinkage or the like is one of the causes of yield deterioration in manufacturing the sensor element and the gas sensor.
On the other hand, when actually used by being mounted on an emission system of an internal combustion in an automobile engine or the like, the gas sensor manufactured with the sensor element is going to be shocked due to various causes. The gas sensor needs strength against shock above a certain level (hereinafter, also referred to merely as strength) so as not to be damaged by such shock.